Concentrations of 0.001, 0.005, 0.01, 0.05 and 0.1 mu-g/ml of fenoxycarb (Ro 13-5223) were applied topically to larvae of Ephestia kuehniella Zeller parasitized by Phanerotoma (Phanerotoma) ocularis Kohl. The effect of the treatment and concentration on parasitism rates, preimaginal mortality and emergence rates of the parasitoid were studied comparatively for each larval instar of the host considered. The preimaginal mortality was high when the fenoxycarb was applied on the first larval instar of the host (23-46%) and more higher when applied to the sixth larval instar of the host (40-86%). Consequently, fenoxycarb treatment of the last larval instar of the host produced a reduction in the emergence rate of the parasitoid. Fenoxycarb treatment of the first larval instar of host reduced the effective parasitism rate by P. ocularis. The effect of the solvent, acetone, was also considered. none